A critical barrier to using enzymes as catalytic human therapeutics against organophosphorous (OP) nerve agents is their poor activity and specificity. Using computational, mechanistic, spectroscopic, and protein mutagenic approaches, we propose the production and optimization of mutants of human enzymes (paraoxonase I, butyrylcholine esterase, and acetylcholinesterase) to catalyze the hydrolysis of chemical warfare nerve agents with greater activity and specificity than those identified to date. Since mutated BuChE, AChE and HuPONI are based on human proteins, the expectation is that these proteins would have few or no immunological and behavioral side effects, making these reasonable human therapeutic candidates. We will elucidate the underlying chemical mechanisms of action necessary for catalytic hydrolysis of chemical warfare nerve agents, design mutants of human proteins with enhanced activity toward nerve agents, and appropriately design recombinant proteins of human origin which can then be expressed in sufficient quantities for subsequent in vivo validation of efficacy. The overall expectation is to develop a sufficient body of scientific data to allow for a selection to be made of one or two protein products for the transition to advanced development as a new generation of prophylactic biological agents with the potential to be granted NDA status and that these biological agents will provide enhanced protection against nerve agent poisoning in a military or civilian setting. Computational, mechanistic, spectroscopic, photoaffinity labeling, mass spectrometric, proteomic, and biochemical tools will be used with wild-type and recombinant mutant forms of cholinesterase and esterase enzymes for the development of these novel therapeutics against organophosphorous (OP) nerve agents. The development of these novel forms of cholinesterase enzymes will provide a biological therapeutic against the use of organophosphorous nerve agents in military and civilian settings. These therapeutics, being of human origin, will have the desired chemical specificity and also few or no immunological and behavioral side effects